On-grid domestic battery storage

thevilla

https://www.shropshirestar.com/news/business/2023/04/26/telford-battery-specialist-breaks-new-ground-with-first-ever-sodium-ion-battery-packs/

Interesting article on a possible cheaper alternative to lithium batteries for home storage.  Less temperature dependent too I understand.

zeupater

Grandad2b said:

Ok, I need a little more information How does high temperature (how high?) affect capacity? Is this effect permanent or just while subjected to the higher temperature? Are all chemistries similarly affected?

zeupater said: ...very low storage capacity ESS setups with relatively high capacity charging equipment.

Some numbers would be helpful. Are you talking about C/2 or lower?

As yet I don't have a battery (is that what you call ESS?) so this is all going to be considered before any purchase decision.

Hi

The issue at hand is the effect of temperature on the irreversible reduction in storage capacity over a given number of cycles ... for example, it seems that over a mere 250 charge cycles, operating lithium batteries at 55C as opposed to 25C results in around 3x the level of irreversible cell degradation (Ah), and that's before the accelerated ageing of associated electronic integrated circuits which should be in line with standard application of the arrhenius predictive methodology modelling which generally predicts an average halving of design life for every additional 10C in operating temperature .... effectively, if the circuit lifespan is designed & calculated at an standard operating temperature of 25C, then the expectation would be that operating that circuit at around 55C would result in a predicted average lifespan of 1/8, therefore a circuit designed for a 25year lifespan would be expected last around 3years ...

In a nutshell the issue is that in looking to improve charging performance slightly in the winter, it's likely that both the batteries and associated electronic circuits will suffer irreparable damage, and that's what I was trying to convey .... if you need to eek out & maximise ESS (Energy Storage System) performance over the short term then there will be a cost over the long term - it's just a case of weighing up one against the other ....

Me? .... considering the cost of the storage, I'd be looking to keep the batteries cool & ensure that the ratio of storage capacity to power input/output favours the energy (kWh) not the power (kW) ... it's the same as EVs really with the temperature conditions for rapid charging and the rate of charge having an impact on the expected cycle life ...

HTH - Z    

orrery

zeupater said:

The issue at hand is the effect of temperature on the irreversible reduction in storage capacity over a given number of cycles ...

An excellent summary. The optimum solution would be to place the battery system in a cool, but not freezing, environment and buy more/bigger batteries to reduce the electrical charge and discharge stress on each one.

Grandad2b

zeupater said:

Grandad2b said:

Ok, I need a little more information How does high temperature (how high?) affect capacity? Is this effect permanent or just while subjected to the higher temperature? Are all chemistries similarly affected?

zeupater said: ...very low storage capacity ESS setups with relatively high capacity charging equipment.

Some numbers would be helpful. Are you talking about C/2 or lower?

As yet I don't have a battery (is that what you call ESS?) so this is all going to be considered before any purchase decision.

Hi

The issue at hand is the effect of temperature on the irreversible reduction in storage capacity over a given number of cycles ... for example, it seems that over a mere 250 charge cycles, operating lithium batteries at 55C as opposed to 25C results in around 3x the level of irreversible cell degradation (Ah), and that's before the accelerated ageing of associated electronic integrated circuits which should be in line with standard application of the arrhenius predictive methodology modelling which generally predicts an average halving of design life for every additional 10C in operating temperature .... effectively, if the circuit lifespan is designed & calculated at an standard operating temperature of 25C, then the expectation would be that operating that circuit at around 55C would result in a predicted average lifespan of 1/8, therefore a circuit designed for a 25year lifespan would be expected last around 3years ...

In a nutshell the issue is that in looking to improve charging performance slightly in the winter, it's likely that both the batteries and associated electronic circuits will suffer irreparable damage, and that's what I was trying to convey .... if you need to eek out & maximise ESS (Energy Storage System) performance over the short term then there will be a cost over the long term - it's just a case of weighing up one against the other ....

Me? .... considering the cost of the storage, I'd be looking to keep the batteries cool & ensure that the ratio of storage capacity to power input/output favours the energy (kWh) not the power (kW) ... it's the same as EVs really with the temperature conditions for rapid charging and the rate of charge having an impact on the expected cycle life ...

HTH - Z    

Thanks for this.

Before I begin can I say I’m not dismissing your opinion but I would like to be sure that I’ve got this in proportion.

In the UK how many days each year does the outside (ambient) temperature go above 25˚C?

How many above 30?

Above 35?

Above 40?

How about low temperatures? I think I mentioned before that some chemistries cannot be charged below 0˚C and that aiui this may shorten their life to zero. I may have misunderstood, I’m not any kind of expert. 

But anyway, how many days does the ambient temperature drop below 5˚C?

Below 0?

Below -5?

Do I need to go on? I frequently wake up to find temperatures below 5˚. Admittedly outside temperature but far more often than I experience temperatures above 30˚

Now, clearly the climate in other parts of the world is different but battery characteristics are standardised at 25 and probably designed to be optimised at that temperature in the same way that cars’ fuel consumption is optimised at 90 and 120 km/h.

Secondly, 250 charge cycles at massively elevated temperature. Where’s this heat coming from? Are the batteries being charged and discharged at high rates? How deep is the charge/discharge cycle? What chemistry is this? Again, someone above gave real life round trip efficiency of about 80% so a 10kWh battery being continuously charged and discharged at C/2 would be wasting about 1kW as heat. This doesn’t sound very likely to be anything close to normal operation but let’s continue with the thought experiment.

It’s a very long time since my Physics A level so I’m not at all confident about modelling heat loss from insulated and uninsulated bodies. Nevertheless, let’s consider the popular Pylontech 3.5kWh battery and stack 3 together to get a capacity of about 10kWh. We’d have a cuboid 420x442x396. It's notable that the middle of the sandwich has to dissipate 333W through just 169224mm^2 where the top and bottom units have more than double that area exposed (an additional 185640mm^2 each). 

The top and bottom units are having to dissipate about 1kW/m^2 but the middle one is about 2kW/m^2. I’d be concerned that this is not a good configuration for these batteries.

Still, I don’t believe this in any way resembles real life usage of domestic battery storage. No doubt there will be times when the battery is required to operate at its rated current but continuously? That’s a commercial or industrial application and should have appropriate cooling. Was this not an issue with the first Nissan Leaf? The cooling system for the battery wasn't adequate. 

Are you sure your comparison with electronics being operated outwith the design parameters is not a red herring? To assume that batteries are engineered with the same characteristics as consumer electronics is absurd. They are made for a global market and our temperate climate is just one of the many they will encounter. 

So, overall is this a real concern? Is low temperature operation? I don’t know. Thanks for your thoughts, I can’t say whether I’ll be seriously considering an ESS but I have more information to weigh on both sides.

[Apologies for the formatting - copied from another application]

1961Nick

Grandad2b said:

zeupater said:

Grandad2b said:

Ok, I need a little more information How does high temperature (how high?) affect capacity? Is this effect permanent or just while subjected to the higher temperature? Are all chemistries similarly affected?

zeupater said: ...very low storage capacity ESS setups with relatively high capacity charging equipment.

Some numbers would be helpful. Are you talking about C/2 or lower?

As yet I don't have a battery (is that what you call ESS?) so this is all going to be considered before any purchase decision.

Hi

The issue at hand is the effect of temperature on the irreversible reduction in storage capacity over a given number of cycles ... for example, it seems that over a mere 250 charge cycles, operating lithium batteries at 55C as opposed to 25C results in around 3x the level of irreversible cell degradation (Ah), and that's before the accelerated ageing of associated electronic integrated circuits which should be in line with standard application of the arrhenius predictive methodology modelling which generally predicts an average halving of design life for every additional 10C in operating temperature .... effectively, if the circuit lifespan is designed & calculated at an standard operating temperature of 25C, then the expectation would be that operating that circuit at around 55C would result in a predicted average lifespan of 1/8, therefore a circuit designed for a 25year lifespan would be expected last around 3years ...

In a nutshell the issue is that in looking to improve charging performance slightly in the winter, it's likely that both the batteries and associated electronic circuits will suffer irreparable damage, and that's what I was trying to convey .... if you need to eek out & maximise ESS (Energy Storage System) performance over the short term then there will be a cost over the long term - it's just a case of weighing up one against the other ....

Me? .... considering the cost of the storage, I'd be looking to keep the batteries cool & ensure that the ratio of storage capacity to power input/output favours the energy (kWh) not the power (kW) ... it's the same as EVs really with the temperature conditions for rapid charging and the rate of charge having an impact on the expected cycle life ...

HTH - Z    

Thanks for this.

Before I begin can I say I’m not dismissing your opinion but I would like to be sure that I’ve got this in proportion.

In the UK how many days each year does the outside (ambient) temperature go above 25˚C?

How many above 30?

Above 35?

Above 40?

How about low temperatures? I think I mentioned before that some chemistries cannot be charged below 0˚C and that aiui this may shorten their life to zero. I may have misunderstood, I’m not any kind of expert. 

But anyway, how many days does the ambient temperature drop below 5˚C?

Below 0?

Below -5?

Do I need to go on? I frequently wake up to find temperatures below 5˚. Admittedly outside temperature but far more often than I experience temperatures above 30˚

Now, clearly the climate in other parts of the world is different but battery characteristics are standardised at 25 and probably designed to be optimised at that temperature in the same way that cars’ fuel consumption is optimised at 90 and 120 km/h.

Secondly, 250 charge cycles at massively elevated temperature. Where’s this heat coming from? Are the batteries being charged and discharged at high rates? How deep is the charge/discharge cycle? What chemistry is this? Again, someone above gave real life round trip efficiency of about 80% so a 10kWh battery being continuously charged and discharged at C/2 would be wasting about 1kW as heat. This doesn’t sound very likely to be anything close to normal operation but let’s continue with the thought experiment.

It’s a very long time since my Physics A level so I’m not at all confident about modelling heat loss from insulated and uninsulated bodies. Nevertheless, let’s consider the popular Pylontech 3.5kWh battery and stack 3 together to get a capacity of about 10kWh. We’d have a cuboid 420x442x396. It's notable that the middle of the sandwich has to dissipate 333W through just 169224mm^2 where the top and bottom units have more than double that area exposed (an additional 185640mm^2 each). 

The top and bottom units are having to dissipate about 1kW/m^2 but the middle one is about 2kW/m^2. I’d be concerned that this is not a good configuration for these batteries.

Still, I don’t believe this in any way resembles real life usage of domestic battery storage. No doubt there will be times when the battery is required to operate at its rated current but continuously? That’s a commercial or industrial application and should have appropriate cooling. Was this not an issue with the first Nissan Leaf? The cooling system for the battery wasn't adequate. 

Are you sure your comparison with electronics being operated outwith the design parameters is not a red herring? To assume that batteries are engineered with the same characteristics as consumer electronics is absurd. They are made for a global market and our temperate climate is just one of the many they will encounter. 

So, overall is this a real concern? Is low temperature operation? I don’t know. Thanks for your thoughts, I can’t say whether I’ll be seriously considering an ESS but I have more information to weigh on both sides.

[Apologies for the formatting - copied from another application]

Sorry to mess up your model but the roundtrip loss energy is split between the battery pack & the inverter. Here are the current numbers from my plant while charging at 2kW (250W/battery):

Ambient 11C
Battery: 19C
Inverter: 37C

The large offset between ambient temperature & inverter temperature suggests that a significant amount of the round trip loss is accounted for there - especially when taking into account the fact that the inverter has heat sinks & is designed to maximise convection cooling.

During winter, operation of the batteries will generate sufficient heat to keep them at a comfortable temperature. Obviously, if the battery is bigger, it will spend less time in standby so the temperature issue becomes smaller. I searched last December's downloads & couldn't find any instances of the battery temperature in single digits even when it'd gone into standby 5 hours before the off peak charge commenced.

Grandad2b

1961Nick said:

Grandad2b said:

zeupater said:

Grandad2b said:

Ok, I need a little more information How does high temperature (how high?) affect capacity? Is this effect permanent or just while subjected to the higher temperature? Are all chemistries similarly affected?

zeupater said: ...very low storage capacity ESS setups with relatively high capacity charging equipment.

Some numbers would be helpful. Are you talking about C/2 or lower?

As yet I don't have a battery (is that what you call ESS?) so this is all going to be considered before any purchase decision.

Hi

The issue at hand is the effect of temperature on the irreversible reduction in storage capacity over a given number of cycles ... for example, it seems that over a mere 250 charge cycles, operating lithium batteries at 55C as opposed to 25C results in around 3x the level of irreversible cell degradation (Ah), and that's before the accelerated ageing of associated electronic integrated circuits which should be in line with standard application of the arrhenius predictive methodology modelling which generally predicts an average halving of design life for every additional 10C in operating temperature .... effectively, if the circuit lifespan is designed & calculated at an standard operating temperature of 25C, then the expectation would be that operating that circuit at around 55C would result in a predicted average lifespan of 1/8, therefore a circuit designed for a 25year lifespan would be expected last around 3years ...

In a nutshell the issue is that in looking to improve charging performance slightly in the winter, it's likely that both the batteries and associated electronic circuits will suffer irreparable damage, and that's what I was trying to convey .... if you need to eek out & maximise ESS (Energy Storage System) performance over the short term then there will be a cost over the long term - it's just a case of weighing up one against the other ....

Me? .... considering the cost of the storage, I'd be looking to keep the batteries cool & ensure that the ratio of storage capacity to power input/output favours the energy (kWh) not the power (kW) ... it's the same as EVs really with the temperature conditions for rapid charging and the rate of charge having an impact on the expected cycle life ...

HTH - Z    

Thanks for this.

Before I begin can I say I’m not dismissing your opinion but I would like to be sure that I’ve got this in proportion.

In the UK how many days each year does the outside (ambient) temperature go above 25˚C?

How many above 30?

Above 35?

Above 40?

How about low temperatures? I think I mentioned before that some chemistries cannot be charged below 0˚C and that aiui this may shorten their life to zero. I may have misunderstood, I’m not any kind of expert. 

But anyway, how many days does the ambient temperature drop below 5˚C?

Below 0?

Below -5?

Do I need to go on? I frequently wake up to find temperatures below 5˚. Admittedly outside temperature but far more often than I experience temperatures above 30˚

Now, clearly the climate in other parts of the world is different but battery characteristics are standardised at 25 and probably designed to be optimised at that temperature in the same way that cars’ fuel consumption is optimised at 90 and 120 km/h.

Secondly, 250 charge cycles at massively elevated temperature. Where’s this heat coming from? Are the batteries being charged and discharged at high rates? How deep is the charge/discharge cycle? What chemistry is this? Again, someone above gave real life round trip efficiency of about 80% so a 10kWh battery being continuously charged and discharged at C/2 would be wasting about 1kW as heat. This doesn’t sound very likely to be anything close to normal operation but let’s continue with the thought experiment.

It’s a very long time since my Physics A level so I’m not at all confident about modelling heat loss from insulated and uninsulated bodies. Nevertheless, let’s consider the popular Pylontech 3.5kWh battery and stack 3 together to get a capacity of about 10kWh. We’d have a cuboid 420x442x396. It's notable that the middle of the sandwich has to dissipate 333W through just 169224mm^2 where the top and bottom units have more than double that area exposed (an additional 185640mm^2 each). 

The top and bottom units are having to dissipate about 1kW/m^2 but the middle one is about 2kW/m^2. I’d be concerned that this is not a good configuration for these batteries.

Still, I don’t believe this in any way resembles real life usage of domestic battery storage. No doubt there will be times when the battery is required to operate at its rated current but continuously? That’s a commercial or industrial application and should have appropriate cooling. Was this not an issue with the first Nissan Leaf? The cooling system for the battery wasn't adequate. 

Are you sure your comparison with electronics being operated outwith the design parameters is not a red herring? To assume that batteries are engineered with the same characteristics as consumer electronics is absurd. They are made for a global market and our temperate climate is just one of the many they will encounter. 

So, overall is this a real concern? Is low temperature operation? I don’t know. Thanks for your thoughts, I can’t say whether I’ll be seriously considering an ESS but I have more information to weigh on both sides.

[Apologies for the formatting - copied from another application]

Sorry to mess up your model but the roundtrip loss energy is split between the battery pack & the inverter. Here are the current numbers from my plant while charging at 2kW (250W/battery):

Ambient 11C
Battery: 19C
Inverter: 37C

The large offset between ambient temperature & inverter temperature suggests that a significant amount of the round trip loss is accounted for there - especially when taking into account the fact that the inverter has heat sinks & is designed to maximise convection cooling.

During winter, operation of the batteries will generate sufficient heat to keep them at a comfortable temperature. Obviously, if the battery is bigger, it will spend less time in standby so the temperature issue becomes smaller. I searched last December's downloads & couldn't find any instances of the battery temperature in single digits even when it'd gone into standby 5 hours before the off peak charge commenced.

So the losses in the battery are smaller? That does mess up the thought experiment somewhat

I guess my concerns about low temp charging are from what I've heard about EVs failing to charge on the granny charger - all the energy was going to heat the battery...

1961Nick

Grandad2b said:

1961Nick said:

Grandad2b said:

zeupater said:

Grandad2b said:

Ok, I need a little more information How does high temperature (how high?) affect capacity? Is this effect permanent or just while subjected to the higher temperature? Are all chemistries similarly affected?

zeupater said: ...very low storage capacity ESS setups with relatively high capacity charging equipment.

Some numbers would be helpful. Are you talking about C/2 or lower?

As yet I don't have a battery (is that what you call ESS?) so this is all going to be considered before any purchase decision.

Hi

The issue at hand is the effect of temperature on the irreversible reduction in storage capacity over a given number of cycles ... for example, it seems that over a mere 250 charge cycles, operating lithium batteries at 55C as opposed to 25C results in around 3x the level of irreversible cell degradation (Ah), and that's before the accelerated ageing of associated electronic integrated circuits which should be in line with standard application of the arrhenius predictive methodology modelling which generally predicts an average halving of design life for every additional 10C in operating temperature .... effectively, if the circuit lifespan is designed & calculated at an standard operating temperature of 25C, then the expectation would be that operating that circuit at around 55C would result in a predicted average lifespan of 1/8, therefore a circuit designed for a 25year lifespan would be expected last around 3years ...

In a nutshell the issue is that in looking to improve charging performance slightly in the winter, it's likely that both the batteries and associated electronic circuits will suffer irreparable damage, and that's what I was trying to convey .... if you need to eek out & maximise ESS (Energy Storage System) performance over the short term then there will be a cost over the long term - it's just a case of weighing up one against the other ....

Me? .... considering the cost of the storage, I'd be looking to keep the batteries cool & ensure that the ratio of storage capacity to power input/output favours the energy (kWh) not the power (kW) ... it's the same as EVs really with the temperature conditions for rapid charging and the rate of charge having an impact on the expected cycle life ...

HTH - Z    

Thanks for this.

Before I begin can I say I’m not dismissing your opinion but I would like to be sure that I’ve got this in proportion.

In the UK how many days each year does the outside (ambient) temperature go above 25˚C?

How many above 30?

Above 35?

Above 40?

How about low temperatures? I think I mentioned before that some chemistries cannot be charged below 0˚C and that aiui this may shorten their life to zero. I may have misunderstood, I’m not any kind of expert. 

But anyway, how many days does the ambient temperature drop below 5˚C?

Below 0?

Below -5?

Do I need to go on? I frequently wake up to find temperatures below 5˚. Admittedly outside temperature but far more often than I experience temperatures above 30˚

Now, clearly the climate in other parts of the world is different but battery characteristics are standardised at 25 and probably designed to be optimised at that temperature in the same way that cars’ fuel consumption is optimised at 90 and 120 km/h.

Secondly, 250 charge cycles at massively elevated temperature. Where’s this heat coming from? Are the batteries being charged and discharged at high rates? How deep is the charge/discharge cycle? What chemistry is this? Again, someone above gave real life round trip efficiency of about 80% so a 10kWh battery being continuously charged and discharged at C/2 would be wasting about 1kW as heat. This doesn’t sound very likely to be anything close to normal operation but let’s continue with the thought experiment.

It’s a very long time since my Physics A level so I’m not at all confident about modelling heat loss from insulated and uninsulated bodies. Nevertheless, let’s consider the popular Pylontech 3.5kWh battery and stack 3 together to get a capacity of about 10kWh. We’d have a cuboid 420x442x396. It's notable that the middle of the sandwich has to dissipate 333W through just 169224mm^2 where the top and bottom units have more than double that area exposed (an additional 185640mm^2 each). 

The top and bottom units are having to dissipate about 1kW/m^2 but the middle one is about 2kW/m^2. I’d be concerned that this is not a good configuration for these batteries.

Still, I don’t believe this in any way resembles real life usage of domestic battery storage. No doubt there will be times when the battery is required to operate at its rated current but continuously? That’s a commercial or industrial application and should have appropriate cooling. Was this not an issue with the first Nissan Leaf? The cooling system for the battery wasn't adequate. 

Are you sure your comparison with electronics being operated outwith the design parameters is not a red herring? To assume that batteries are engineered with the same characteristics as consumer electronics is absurd. They are made for a global market and our temperate climate is just one of the many they will encounter. 

So, overall is this a real concern? Is low temperature operation? I don’t know. Thanks for your thoughts, I can’t say whether I’ll be seriously considering an ESS but I have more information to weigh on both sides.

[Apologies for the formatting - copied from another application]

Sorry to mess up your model but the roundtrip loss energy is split between the battery pack & the inverter. Here are the current numbers from my plant while charging at 2kW (250W/battery):

Ambient 11C
Battery: 19C
Inverter: 37C

The large offset between ambient temperature & inverter temperature suggests that a significant amount of the round trip loss is accounted for there - especially when taking into account the fact that the inverter has heat sinks & is designed to maximise convection cooling.

During winter, operation of the batteries will generate sufficient heat to keep them at a comfortable temperature. Obviously, if the battery is bigger, it will spend less time in standby so the temperature issue becomes smaller. I searched last December's downloads & couldn't find any instances of the battery temperature in single digits even when it'd gone into standby 5 hours before the off peak charge commenced.

So the losses in the battery are smaller? That does mess up the thought experiment somewhat

I guess my concerns about low temp charging are from what I've heard about EVs failing to charge on the granny charger - all the energy was going to heat the battery...

I don't know for sure if the losses are mainly in the inverter but the temperature mine runs at suggests that the loss is significant.

My inverter app (Solarman) is currently showing a lifetime difference of 10.6% between charge & discharge energy. I have a meter fitted to the inverter which is showing a 20.9% loss. The additional 10.3% could be losses in the inverter whereas the app could just be measuring the difference between the energy sent to & received from the battery pack?

EV batteries will have a considerably greater opportunity to cool down - generally parked outside & used only for brief periods.

zeupater

Grandad2b said:

zeupater said:

Grandad2b said:

Ok, I need a little more information How does high temperature (how high?) affect capacity? Is this effect permanent or just while subjected to the higher temperature? Are all chemistries similarly affected?

zeupater said: ...very low storage capacity ESS setups with relatively high capacity charging equipment.

Some numbers would be helpful. Are you talking about C/2 or lower?

As yet I don't have a battery (is that what you call ESS?) so this is all going to be considered before any purchase decision.

Hi

The issue at hand is the effect of temperature on the irreversible reduction in storage capacity over a given number of cycles ... for example, it seems that over a mere 250 charge cycles, operating lithium batteries at 55C as opposed to 25C results in around 3x the level of irreversible cell degradation (Ah), and that's before the accelerated ageing of associated electronic integrated circuits which should be in line with standard application of the arrhenius predictive methodology modelling which generally predicts an average halving of design life for every additional 10C in operating temperature .... effectively, if the circuit lifespan is designed & calculated at an standard operating temperature of 25C, then the expectation would be that operating that circuit at around 55C would result in a predicted average lifespan of 1/8, therefore a circuit designed for a 25year lifespan would be expected last around 3years ...

In a nutshell the issue is that in looking to improve charging performance slightly in the winter, it's likely that both the batteries and associated electronic circuits will suffer irreparable damage, and that's what I was trying to convey .... if you need to eek out & maximise ESS (Energy Storage System) performance over the short term then there will be a cost over the long term - it's just a case of weighing up one against the other ....

Me? .... considering the cost of the storage, I'd be looking to keep the batteries cool & ensure that the ratio of storage capacity to power input/output favours the energy (kWh) not the power (kW) ... it's the same as EVs really with the temperature conditions for rapid charging and the rate of charge having an impact on the expected cycle life ...

HTH - Z    

Thanks for this.

Before I begin can I say I’m not dismissing your opinion but I would like to be sure that I’ve got this in proportion.

In the UK how many days each year does the outside (ambient) temperature go above 25˚C?

How many above 30?

Above 35?

Above 40?

How about low temperatures? I think I mentioned before that some chemistries cannot be charged below 0˚C and that aiui this may shorten their life to zero. I may have misunderstood, I’m not any kind of expert. 

But anyway, how many days does the ambient temperature drop below 5˚C?

Below 0?

Below -5?

Do I need to go on? I frequently wake up to find temperatures below 5˚. Admittedly outside temperature but far more often than I experience temperatures above 30˚

Now, clearly the climate in other parts of the world is different but battery characteristics are standardised at 25 and probably designed to be optimised at that temperature in the same way that cars’ fuel consumption is optimised at 90 and 120 km/h.

Secondly, 250 charge cycles at massively elevated temperature. Where’s this heat coming from? Are the batteries being charged and discharged at high rates? How deep is the charge/discharge cycle? What chemistry is this? Again, someone above gave real life round trip efficiency of about 80% so a 10kWh battery being continuously charged and discharged at C/2 would be wasting about 1kW as heat. This doesn’t sound very likely to be anything close to normal operation but let’s continue with the thought experiment.

It’s a very long time since my Physics A level so I’m not at all confident about modelling heat loss from insulated and uninsulated bodies. Nevertheless, let’s consider the popular Pylontech 3.5kWh battery and stack 3 together to get a capacity of about 10kWh. We’d have a cuboid 420x442x396. It's notable that the middle of the sandwich has to dissipate 333W through just 169224mm^2 where the top and bottom units have more than double that area exposed (an additional 185640mm^2 each). 

The top and bottom units are having to dissipate about 1kW/m^2 but the middle one is about 2kW/m^2. I’d be concerned that this is not a good configuration for these batteries.

Still, I don’t believe this in any way resembles real life usage of domestic battery storage. No doubt there will be times when the battery is required to operate at its rated current but continuously? That’s a commercial or industrial application and should have appropriate cooling. Was this not an issue with the first Nissan Leaf? The cooling system for the battery wasn't adequate. 

Are you sure your comparison with electronics being operated outwith the design parameters is not a red herring? To assume that batteries are engineered with the same characteristics as consumer electronics is absurd. They are made for a global market and our temperate climate is just one of the many they will encounter. 

So, overall is this a real concern? Is low temperature operation? I don’t know. Thanks for your thoughts, I can’t say whether I’ll be seriously considering an ESS but I have more information to weigh on both sides.

[Apologies for the formatting - copied from another application]

Hi

I believe you're overthinking and misunderstanding ....

In your earlier postulation it seems you were considering somehow insulating an ESS so as to increase the operating temperature to take advantage of a better charging curve during the winter ... the information provided is simply a caution on doing this as it would likely shorten the useful life of the ESS itself & it would be up to you to decide whether this approach would be appropriate to your own position and requirements ....

As for ambient conditions, well that's not the issue, it's the operating temperature of the batteries themselves that is important, and the very fact that you'd be looking to artificially increase that temperature through adding insulation and/or airflow reduction that would be more problematic .... keeping the heat in when the manufacturer has designed the system for heat dissipation wouldn't seem to be a very logical step, nor would choosing to site an ESS in a loft where the ambient temperature in the summer could well reach temperatures ~55C. As mentioned in the previous post, raising the battery cell operating temperature has a detrimental effect of longevity, this has been measured and is the subject of numerous published articles in scientific journals - the 3x faster degradation figure is something I picked up on some time ago and was part of a published study involving various charge cycles & temperatures, but if you want to disagree it's relevance, well that's down to yourself & the decisions you are looking to make, but it doesn't mean the paper's findings were irrelevant in any way ...

What you need to appreciate is that in discussions related to electrical & electronic equipment efficiencies, the inefficiencies are normally directly related to energy conversion into a waste product as a result of resistance, so normally heat ... that's why the laptop I'm using often gets much hotter than the ambient temperature of the room and that's why the design of the equipment includes a fan to protect against premature temperature related electronic component failure ... if I were to deliberately restrict the airflow the anticipated lifespan of some major components would likely fall from an average of multiple decades to mere days or hours. In questioning whether this this would be considered a 'red herring' within battery storage because they're different to 'consumer electronics' you seem to be missing the fact that the ESS contains 'consumer electronics' circuitry in the form of bms, communication, control etc so that's effectively what you have ... consumer electronics packaged amongst and connected to a number of battery packs within an enclosure, so no, it's not a 'red herring', it's fundamental

The question you should be asking is how do manufacturers of electronic components have a clue to lifespans being in the region of decades when none of their components have been tested for decades due to the fact that the technology isn't old enough ... well that's where accelerated lifespan testing at elevated temperatures comes into play, they model & test for failure according to some pretty advanced formulae, however, whatever they use generally conforms to the arrhenius predictive findings, so somewhere around a halving of lifespan for each additional 10C of operating temperature ... okay, it's a rule of thumb, but it's one that generally works & should be considered good enough to get an idea through to someone or quickly test assumptions ... again, it's up to you to accept or not accept the answers to questions you are seeking from others, but it's generally considered good practice to openly research the validity of any offered answers prior to subjecting them to dispute just because they conflict with a preset positional bias, if you're not open to entertain answers to posed questions, then why seek answers in the first place ... 

As for the heatloss example, it's not the heatloss that you need to look at, it's the level of heat retention given a level of heat generation at various levels of insulation under consideration. Heatloss under whatever conditions is a function of the DeltaT between ambient & whatever needs cooling, the heat source is in this case a function of the inefficiencies within the ESS and the resistance to heat transfer would be a function of the original enclosure design PLUS the effective U value of the additional insulation you'd be looking to add to the installation ... effectively, adding insulation simply results in raising the DeltaT between the ESS internal components within the insulated bubble and the ambient temperature to a point where temperature (/energy) input & output reach equilibrium .... it's this raised DeltaT that will impact on the anticipated lifespan of the ESS, with the added possibility of creating a very real fire hazard potential.

Finally, in terms of electronic circuitry & lithium battery physical operating temperatures, 55C should not be considered to be anywhere near a 'massively elevated temperature' ... as mentioned earlier, conditions similar to this could be considered to be regularly achievable as ambient for some locations even in the UK, such as a loft, so add in a considerable number of Ohms as an internal heat source and the equipment temperature will be elevated well above 55C even with an unmodified installation.

HTH - Z

orrery

I think that the discussion moved in response to my asking whether siting a system in the loft was a wise move given the elevated temperatures in some lofts - mine is completely unbearable for long periods in mid summer. My point was that my garage (attached to the house) has a much more hospitable temperature range - never going below zero and being reasonably cool (comparatively) in summer. So, I was merely pointing out that there may be, in some cases, good technical reasons to install solar and battery systems in a garage rather than a loft. A system in a garage is also more maintainable than one in a loft.

* other peoples lofts and garages may vary

orrery

Grandad2b said:

Again, someone above gave real life round trip efficiency of about 80% so a 10kWh battery being continuously charged and discharged at C/2 would be wasting about 1kW as heat. This doesn’t sound very likely to be anything close to normal operation but let’s continue with the thought experiment.

I have x4 Pylontech US5000 is a server rack, enclosed with a glass door on the front. I have never been able to detect any rise in temperature on the batteries (by placing my hand on the top and bottom of the battery) - they appear stone cold at all times to me.

The inverter is passively cooled and does get warm.